Two-dimensional solid phase assay

A method for assaying a substance is provided in which an optical image is obtained from spots of light emitted from a chemiluminescent material capable of undergoing a luminescent reaction. The method comprises: (a) a step of distributing solid particles on the surface of a support, the solid particles having a diameter of not more than 100 mu m and on its surface carrying an antibody being able to catch a catalyst previously bound to the second antibody (or its analogue, such as Fab') through binding an antigen, and the support being permeable to a liquid and capable of absorbing light emitted from chemiluminescent material; (b) a step of immersing the support into a solution containing the chemiluminescent material to bring the catalyst over the support into contact with the chemiluminescent material to cause luminescent reactions including fluorescence; (c) a step of two-dimensionally picking up an optical image including an image formed by luminescence and fluorescence, and converting it into electric signals; (d) a step of storing the measured two-dimensional image data of the optical image in a image processing device; and (e) a step of manipulating the stored signals to form a new image in the same processing device.